Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Including integrally formed optical element
Reexamination Certificate
2000-05-16
2001-10-23
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Including integrally formed optical element
C438S016000, C186S002000, C186S002000
Reexamination Certificate
active
06306674
ABSTRACT:
FIELD OF THE INVENTION
The field of the invention is the field of semiconductor processing, and in particular to the field of multilayer compound semiconductor processing.
BACKGROUND OF THE INVENTION
The background of the invention is given in great detail in the above identified applications.
A schematic drawing of the prior art fabrication procedure for a monolithic array of semiconductor laser diodes is shown in
FIG. 1. A
substrate
2
of n-type GaAs material has a number of layers grown epitaxially. The important cladding layers
6
of n-type AlGaAs and
7
of p-type AlGaAs surround an active layer
4
which normally has a lower bandgap than the cladding layers and may be composed of many layers of AlGaAs, GaAs, InGaAs, or other III-V semiconductor compounds. A layer of exposed and developed photoresist
8
is shown with openings
9
etched in the photoresist. Step b of the prior art procedure uses an etching step to etch vee grooves in the cladding layer
7
, generally through the active layer
4
and into the other cladding layer
6
. A blanket layer of insulating material
12
such as SiO2 is then deposited on the substrate. This step generally requires heating the wafer which can increase the defects generated by heating and cooling the many layers of different material. Another layer of photoresist is then deposited on the wafer, and is exposed and developed in an expensive alignment procedure to give the photoresist portions
14
covering the vee grooves
10
. The SiO2 is then etched away from the areas between the vee grooves
10
, the photoresist is stripped, and blanket metalization layers
18
and
20
are deposited over the front side and the back side of the wafer. The remaining oxide isolates each laser diode from its neighbor. In contrast, the fabrication of a monolithic array of semiconductor laser diodes using the method of U.S. application Ser. No. 08/339,811 filed Nov. 15, 1994 (Now U.S. pat. No. 5,559,058) cited above is shown in
FIG. 2
, where pulsed anodic oxidization is used to produce trenches
22
covered with native oxide
24
, saving the expensive lithography step of the prior art.
OBJECTS OF THE INVENTION
It is an object of the invention to monitor the electrical parameters and optical parameters of pulsed and continuous production of oxide and other layers on a multilayer compound semiconductor surface.
It is an object of the invention to monitor the depth of etching of material from the surface of a multilayer compound semiconductor surface.
It is the object of the invention to etch a multilayer compound semiconductor surface to a precise depth with respect to the multilayer structure.
SUMMARY OF THE INVENTION
The current passed between a conducting fluid and the surface of a multilayer compound semiconductor surface is a function of the thickness of an oxide built up on the surface and of the particular parameters of the multilayer structure. In the case that a “traveling oxide” or other product of a reaction is formed by simultaneous or sequential production and dissolution of the reaction product, the reaction may be monitored by monitoring the electrical and optical properties of the surface, and the reaction may be stopped precisely at an optimum point for semiconductor device production.
REFERENCES:
patent: 5480511 (1996-01-01), Barbee et al.
Berry Renee R.
Hodgson Rodney T.
Nelms David
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